Intervertebral spacers and related methods and instruments

ABSTRACT

Biomedical implants comprising portions made of disparate materials such as intervertebral implants and related methods and instruments. In some embodiments, the implant may comprise a base portion comprising a first material and a secondary fastener portion comprising a second material having distinct physical properties relative to the first material. The secondary portion may wholly define a front end wall surface of the implant, and the base portion and the secondary portion may collectively define at least one of an upper surface and a lower surface of the implant.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/002,714 filed on Jun. 7, 2018, and titled “INTERVERTEBRAL SPACERS ANDRELATED METHODS AND INSTRUMENTS, which is a continuation of U.S. patentapplication Ser. No. 14/801,665 filed on Jul. 16, 2015, and titled“INTERVERTEBRAL SPACERS AND RELATED METHODS AND INSTRUMENTS” whichclaims the benefit of priority of U.S. Provisional Patent ApplicationNo. 62/025,444 filed Jul. 16, 2014 and titled “INTERVERTEBRAL SPACERSAND RELATED METHODS AND INSTRUMENTS”. The aforementioned applicationsare hereby incorporated by reference herein in their entireties.

SUMMARY

Various embodiments of apparatus, methods, and systems are disclosedherein that relate to biomedical implants and instruments for installingsuch implants. In preferred embodiments and implementations, thebiomedical implants comprise spinal implants. For example, someembodiments may comprise stand-alone anterior lumbar interbody (ALIF)fusion implants. Some embodiments may comprise instruments forinstalling such intervertebral spinal implants, including inserters,instrument guide tubes, instrument guide tube handles, flexibleinstruments and instrument tips, and screw driver tips. However, itshould be understood that many of the concepts disclosed herein may beapplied to other intervertebral spinal implants, including thosedesigned for ALIF fusion with pedicle screws or other fixationmechanisms, for posterior lumbar interbody fusion (PLIF), fortransforaminal lumbar interbody fusion (TLIF), for direct lateralinterbody fusion (DLIF), and the like. Moreover, still other principles,components, elements, and/or features disclosed herein may be applicableto other biomedical implants.

In some preferred embodiments, different types of materials may becombined in a single implant. For example, a relatively non-threadabiematerials and/or a material capable of having relatively lessstrong/stabile threads may be used for a base portion of an implant andone or more plates, sleeves, inserts, or other secondary portion(s) ofan implant may comprise a more readily threadable material and/or amaterial capable of having relatively more strong/stabile threads. Suchconfigurations may be useful in that they allow for use of a more easilythreadable material for receipt of bone screws, or a material that willmore readily receive/accept screws, along with another material withother, more desirable characteristics for serving as the primary or baseportion of an intervertebral implant.

In a more particular example of an intervertebral spinal implant, suchas in some embodiments a standalone anterior lumbar interbody fusionimplant, according to some embodiments, the implant may comprise a baseportion comprising a first material and a secondary portion comprising asecond material, wherein the second material is distinct from the firstmaterial. The second material preferably has distinct physicalproperties relative to the first material. In some embodiments, thesecondary portion may wholly define a front end wall surface of theintervertebral spinal implant, and the base portion and the secondaryportion may collectively define at least one of an upper surface and alower surface of the intervertebral spinal implant. In some embodiments,the base portion and the secondary portion may collectively define boththe upper surface and the lower surface of the implant.

Some embodiments may further comprise a locking member for coupling thebase portion to the secondary portion. Some such embodiments may furthercomprise a second locking member for coupling the base portion to thesecondary portion. In some such embodiments, the base portion may atleast partially (in some embodiments, fully) define a first sidewall ofthe spinal implant and at least partially (in some embodiments, fully)define a second sidewall of the spinal implant opposite from the firstsidewall. Thus, the locking member may be configured to couple thesecondary portion to the base portion at the first sidewall, and at thesecond sidewall.

In some embodiments, the secondary portion may comprise at least onethreaded bone screw opening configured to receive a bone screwtherethrough.

In another example of an intervertebral spinal implant, according tocertain preferred embodiments, the implant may comprise a base portioncomprising a first material. The base portion may comprise an opening.The implant may further comprise a secondary fastener portion comprisinga second material, wherein the second material is distinct from thefirst material, and wherein the second material has distinct physicalproperties relative to the first material. The secondary fastenerportion may be configured to be received in the opening, and may furtherbe configured to engage with a fastener such that the secondary fastenerportion is positioned in between the fastener and the base portion. Someembodiments may comprise a plurality of secondary fastener portionsconfigured to be received in a plurality of openings formed within thebase portion.

In some embodiments, the fastener or fasteners may comprise a bone screwconfigured to extend through the intervertebral spinal implant andengage a vertebral body of a patient's spine.

In some embodiments, the secondary fastener portion(s) may be configuredto prevent contact between the fastener and the base portion.

In some embodiments, the secondary fastener portion(s) may comprise aninternal thread in some such embodiments, the internal thread may extendabout an internal periphery of the secondary fastener portion(s) betweenabout one turn and about two turns. In some such embodiments, theinternal thread may extend about this internal periphery by about oneturn.

In some embodiments, the secondary fastener portion may comprise anengagement feature configured to engage with a corresponding engagementfeature of the base portion. In some such embodiments, the engagementfeature of the fastener portion may comprise a protruding rim, and theengagement feature of the base portion may comprise a slot formed withinthe opening, or vice versa.

In some embodiments, the secondary fastener portion may comprise meansfor preventing the secondary fastener portion from rotating with respectto the base portion, such as a protrusion formed on the secondaryfastener portion configured to be received in a groove formed within thebase portion, or vice versa.

In another example of a spinal implant according to certain embodiments,the implant may comprise a base portion comprising a first material. Thebase portion may at least partially define a first sidewall of thespinal implant, and may further at least partially define a secondsidewall of the spinal implant opposite from the first sidewall. Thebase portion may wholly define a first end wall of the spinal implant,and the base portion may lack an end wall opposite from the first endwall. The implant may further comprise a secondary portion comprising asecond material that is distinct from the first material and hasdistinct physical properties relative to the first material. Thesecondary portion may be coupled to the base portion at the firstsidewall and at the second sidewall such that the secondary portion atleast partially defines a second end wall of the spinal implant oppositefrom the first end wall. In some embodiments, the secondary portion maywholly define the second end wall.

In some embodiments, the secondary portion may bridge a gap between afirst end of the first sidewall and a first end of the second sidewallof the base portion so as to wholly define the second end wall. In somesuch embodiments, the base portion may at least substantially comprise a“C” shape.

The features, structures, steps, or characteristics disclosed herein inconnection with one embodiment may be combined in any suitable manner inone or more alternative embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The written disclosure herein describes illustrative embodiments thatare non-limiting and non-exhaustive. Reference is made to certain ofsuch illustrative embodiments that are depicted in the figures, inwhich:

FIG. 1 is a perspective view of an embodiment of a stand-alone anteriorlumbar interbody fusion spinal implant.

FIG. 2 is an exploded perspective view of the spinal implant of FIG. 1.

FIG. 3 is an exploded perspective view of another embodiment of astand-alone anterior lumbar interbody fusion spinal implant.

FIG. 4 is a perspective view of the spinal implant of FIG. 3.

FIG. 5 is an exploded perspective view of still another embodiment of astand-alone anterior lumbar interbody fusion spinal implant.

FIG. 6 is an exploded perspective view of yet another embodiment of astand-alone anterior lumbar interbody fusion spinal implant.

FIG. 7 is an exploded perspective view of still another embodiment of astand-alone anterior lumbar interbody fusion spinal implant.

FIG. 8 is a perspective view of the spinal implant of FIG. 7.

FIG. 9 is a close-up view of one side of a coupling between the baseportion and the secondary portion of the spinal implant of FIGS. 7 and8.

FIG. 10 is an exploded perspective view of yet another embodiment of astand-alone anterior lumbar interbody fusion spinal implant.

FIG. 11 is a perspective view of the spinal implant of FIG. 10.

FIG. 12 is an elevation view of an embodiment of a locking screwconfigured for use with certain embodiments of spinal implants.

FIG. 13 is a close-up perspective view of a fastener opening of a spinalimplant comprising locking features configured for engaging acorresponding locking fastener.

FIG. 14 is a perspective view of an embodiment of an inserter tool thatmay be used to install screws and/or fasteners into one or more of thespinal implants disclosed herein.

FIG. 15 is a close-up view of a distal tip of another embodiment of aninserter tool.

FIG. 16 is a perspective view of a distal end of an embodiment of aguide tube that may be used in connection with an inserter tool toinstall screws and/or fasteners into one or more of the spinal implantsdisclosed herein.

FIG. 17 is a perspective view of the entire guide tube of FIG. 16.

FIG. 18 is a perspective view of an embodiment of a flexible driverinstrument that may be used in connection with one or more of the guidetubes and/or inserter tools disclosed herein to install screws and/orfasteners into one or more of the spinal implants disclosed herein.

FIG. 19 is a phantom, perspective view of an embodiment of an instrumentcomprising a combined guide tube and flexible driver.

FIG. 20 is a phantom, perspective view of the instrument of FIG 19, butillustrated in a retracted position with a bone screw retracted into theguide tube portion of the combined instrument.

FIG. 21 is an exploded, perspective view of another embodiment of astand-alone anterior lumbar interbody fusion spinal implant with a baseportion of the implant shown in phantom.

FIG. 22A is a perspective view of yet another embodiment of astand-alone anterior lumbar interbody fusion spinal implant.

FIG. 22B is an exploded, perspective view of the implant of FIG. 22A.

FIG. 23 is a cross-sectional view taken along line 23-23 in FIG. 22A.

FIG. 24 is a perspective view of an embodiment of a secondary fastenermember comprising a sleeve.

FIG. 25 is a perspective view of an alternative embodiment of asecondary fastener member comprising a sleeve.

FIG. 26 is a perspective view of still alternative embodiment of asecondary fastener member comprising a sleeve.

FIG. 27 is an exploded, perspective view of another embodiment of astand-alone anterior lumbar interbody fusion spinal implant.

FIG. 28 is an exploded, perspective view of still another embodiment ofa stand-alone anterior lumbar interbody fusion spinal implant.

FIG. 29 is an exploded, perspective view of yet another embodiment of astand-alone anterior lumbar interbody fusion spinal implant.

DETAILED DESCRIPTION

It will be readily understood that the components of the presentdisclosure, as generally described and illustrated in the drawingsherein, could be arranged and designed in a wide variety of differentconfigurations. Thus, the following more detailed description of theembodiments of the apparatus is not intended to limit the scope of thedisclosure, but is merely representative of possible embodiments of thedisclosure In some cases, well-known structures, materials, oroperations are not shown or described in detail.

Various embodiments of apparatus, methods, and systems are disclosedherein that relate to intervertebral spinal implants and instruments forinstalling such implants. For example, some embodiments may comprisestand-alone anterior lumbar interbody (ALIF) fusion implants. Someembodiments may comprise instruments for installing such intervertebralspinal implants, including inserters, instrument guide tubes, instrumentguide tube handles, flexible instruments and instrument tips, and screwdriver tips. However, it should be understood that many of the conceptsdisclosed herein may be applied to other intervertebral spinal implants,including those designed for ALIF fusion with pedicle screws or otherfixation mechanisms, for posterior lumbar interbody fusion (PLIF), fortransforaminal lumbar interbody fusion (TLIF), for direct lateralinterbody fusion (DLIF), and the like.

In some embodiments, different types of materials may be combined in asingle implant For example, a ceramic material, such as a siliconnitride ceramic material, may be used for a base portion of an implantand one or more plates, sleeves, inserts, or other secondary portion(s)of an implant may comprise another material or materials, such astitanium another metal, or a plastic, such as PEEK, for example. Suchconfigurations may be useful in that they allow for use of a more easilythreadable material for receipt of bone screws, or a material that willmore readily receive/accept screws, along with another material withother, more desirable characteristics for serving as the primary or baseportion of an intervertebral implant, such as silicon nitride ceramic,another ceramic, or another material having distinct properties relativeto the other portion of the device.

Examples of suitable silicon nitride materials are described in, forexample, U.S. Pat. No 6,881,229, titled “Metal-Ceramic CompositeArticulation,” which is incorporated by reference herein. In someembodiments, dopants such as alumina (Al₂O₃), yttria (Y₂O₃), magnesiumoxide, and strontium oxide, can be processed to form a doped compositionof silicon nitride. In some embodiments, powders of silicon nitride maybe used to form the ceramic implants, either alone or in combinationwith one or more of the dopants referenced above. Other examples ofsuitable silicon nitride materials are described in U.S. Pat. No.7,666,229 titled “Ceramic-Ceramic Articulation Surface Implants,” whichis hereby incorporated by reference. Still other examples of suitableSilicon Nitride materials are described in U.S. Pat. No. 7,695,521titled “Hip Prosthesis with Monoblock Ceramic Acetabular Cup.” which isalso hereby incorporated by reference.

Additional details regarding certain preferred embodiments will now bedescribed in greater detail with reference to the accompanying drawings.FIG. 1 depicts a perspective view of an embodiment of a standalone ALIFimplant 100. Implant 100 comprises a base portion 110 and a secondaryportion 150. Base portion 110 and secondary portion 150 preferablycomprise different materials such that implant 100 may take advantage ofthe different characteristics of the two different materials in the sameimplant. For example, in some embodiments, base portion 110 may comprisea silicon nitride ceramic material or another similar ceramic material.Secondary portion 150 may comprise a metal, such as a titanium metal ortitanium alloy.

Base portion 110 of implant 100 comprises an upper surface 102, a lowersurface 104, a first side wall surface 106, a second side wall surface108 opposite from surface 106, a front end wall surface 112, and a rearend wall surface 114 opposite from front end wall surface 112. Front endwall surface 112 comprises a recess configured to facilitate couplingwith secondary portion 150.

Upper and lower surfaces 102 and 104 may both comprise a plurality ofengagement structures 120, which, in the depicted embodiment, compriserows of teeth. Teeth 120 may be arranged in parallel rows that may eachextend at least substantially perpendicular to the direction in whichside wall surfaces 106 and 108 extend.

Upper surface 102 also comprises an opening 122. Opening 122 alsoextends through lower surface 104 to allow for ingrowth of bony materialtherethrough. As those of ordinary skill in the art will appreciate,other embodiments are contemplated in which multiple such openingsextend between upper surface 102 and lower surface 104.

In the depicted embodiment of FIGS. 1 and 2, secondary portion 150comprises an insert configured to receive fasteners, such as bonescrews, therethrough. Other types of fasteners that may be usable withone or more of the embodiments disclosed herein may include dowels,pins, nails, pegs, and expandable screws/pegs/pins, etc. Thus, secondaryportion 150 may be considered a secondary fastener portion or an insert.Insert 150 comprises three fastener openings, namely, fastener openings152, 154, and 156. Each of these fastener openings may be configured toreceive a bone screw (not shown) or another such fastener. Fasteneropenings 152, 154, and 156 may be threaded in some embodiments.

Fastener opening 152 extends from a surface 151 of secondary portion 150that is configured to smoothly transition with front end wall surface112 of base portion 110. Thus, implant 100 comprises a front end wallsurface defined in part by front end wall surface 112 of base portion110 and surface 151 of secondary portion 150. As best seen in FIG. 1,fastener opening 152 is configured to direct a screw or other fastenerthrough upper surface 102. In alternative embodiments, however, one ormore surfaces of implant 100 may be fully-defined by secondary portion150. Thus, in alternative embodiments, front end wall surface 112 may befully defined by surface 151 of secondary portion 150.

As also depicted in FIG. 1, secondary portion 150 further comprises atab 160. Tab 160 is configured to engage base portion 110 to securesecondary portion 150 to base portion 110. In alternative embodiments,however, one or more such tabs may instead be formed on base portion 110and be configured to engage a structure or other part of secondaryportion 150. In the depicted embodiment tab 160 is configured to extendover and engage a part of base portion 110 that defines opening 122. Insome embodiments, multiple tabs may be used to facilitate suchsecurement.

As shown in FIGS. 1 and 2, tab 160 may comprise a hook-shaped end 161 tofurther facilitate engagement with base portion 110. In addition, insome embodiments, a corresponding recess, depression, and/or matingfeature may be formed on base portion 110 to provide for a more secureengagement. Tab 160 may also be flexible to allow it to flex away fromand then resiliently flex towards base portion 110. Tab 160 may also beformed from the surface/material defining fastener opening 152.

More particularly, in the depicted embodiment, as best seen in theexploded view of FIG. 2, tab 160 is at least partially defined by twoparallel slits 162 formed within the material defining fastener opening152. This may allow tab 160 to flex into and away from fastener opening152, which may allow for hook-shaped portion 161 to flex away from andresiliently engage base portion 110. Because another portion ofsecondary portion 150 engages an opposite surface of base portion 110,as described in greater detail below, a single tab 160 may providesufficient force to keep these two pieces securely engaged to oneanother. However, as previously mentioned, other embodiments arecontemplated in which multiple tabs may be used.

Fastener openings 154 and 156 are best seen in FIG. 2. As seen in thisfigure, fastener openings 154 and 156 are partial holes. In other words,fastener openings 154 and 156 comprise in cross section only partial,unclosed circles, ovals, or the like. However, these openings may besufficiently near fully closed in order to hold screws or otherfasteners in place. Still, should be understood that other embodimentsare contemplated in which these fasteners comprise fully-closed holes.

Fastener openings 154 and 156 may be configured to engage recesses 124and 126, respectively, formed within base portion 10. Thus, after tab160 has been engaged with base portion 110, as shown in FIG. 1, tab 160may be configured to resiliently bias recesses 124 and 126 againstportions of secondary portion 150 that define fastener openings 154 and156.

As also depicted in FIG. 2, secondary portion 150 may comprise a lowersurface 164 comprising teeth 165 positioned on op posit sides offastener openings 154 and 156. Teeth 165 may be configured to be alignedwith teeth 120 when secondary portion 150 has been engage with baseportion 110. Similarly, secondary portion 150 may comprise an uppersurface 166 comprising teeth 167 positioned in opposite sides offastener opening 152, as shown in FIG. 1. As also shown in FIG. 1, teeth167 may be configured to align with teeth 120 of base portion 110 whenbase portion has been engaged with secondary portion 150.

As depicted in FIG. 2, teeth 120 in upper surface 102 may be partiallypositioned on an island 105 positioned in between the two side wallsurfaces 106 and 108. The teeth on island 105 may be configured to matchand align with corresponding teeth 185 positioned interiorly withrespect to and adjacent to fastener openings 154 and 156.

Rear end wall surface 114 may comprise a centrally-located concavity113, as depicted in FIGS. 1 and 2. Concavity 113 may be configured toaccommodate a patient's spinal cord or otherwise conform to certainanatomical features of a spinal column.

FIGS. 3 and 4 depict an alternative embodiment of a stand-alone ALIFimplant 300. Implant 300 comprises a base portion 310 and a plurality ofsecondary fastener portions 350 a-c. Base portion 310 and secondaryfastener portions 350 a, 350 b, and 350 c, respectively, preferablycomprise different materials such that implant 300 may take advantage ofthe different characteristics of the two different materials in the sameimplant. For example, in some embodiments, base portion 310 may comprisea silicon nitride ceramic material or another similar ceramic materialand secondary fastener portions 350 a-c may each comprise a metal, suchas a titanium metal or titanium alloy.

Base portion 310 comprises an upper surface 302, a lower surface 304, afirst side wall surface 306, a second side wall surface 308 oppositefrom surface 306, a front end wall surface 312, and a rear end wallsurface 314 opposite from front end wall surface 312. Front end wallsurface 312 comprises three recesses 315 a-c configured to facilitatecoupling with secondary fastener portions 350 a-c, respectively. Rearend wall surface 314 comprises a centrally-located concavity 313, whichmay be configured to accommodate a patient's spinal cord or otherwiseconform to certain anatomical features of a spinal column.

In the embodiment of FIGS. 3 and 4, secondary fastener portions 350 a-ceach comprise sleeves configured to engage with a single screw or otherfastener and facilitate coupling of such fastener/screw with baseportion 310. More particularly, as shown in FIG. 3, bone screws 10 areconfigured to each fit within a corresponding sleeve 350. Two of thebone screws 10 are configured to extend through one of the two opposingsurfaces for contacting vertebrae (in the depicted embodiment, lowersurface 304), and one of the bone screws 10 is configured to extendthrough an opposite surface (in the depicted embodiment, upper surface302). However, a wide variety of alternative embodiments arecontemplated in which any desired number of fasteners extending throughany of the various surfaces may be used.

Upper surface 302 comprises an opening 322 that extends through lowersurface 304 to allow for ingrowth of bony material therethrough. Upperand lower surfaces 302 and 304 may both comprise a plurality ofengagement structures 320, which, in the depicted embodiment, compriserows of teeth. Teeth 320 may be arranged in parallel rows that may eachextend at least substantially perpendicular to the direction in whichside wall surfaces 306 and 308 extend.

In the embodiment of FIGS. 3 and 4, sleeves 350 a-c are each configuredto be received in a sleeve recess formed within base portion 310. Insome embodiments, sleeves 350 a-c may be threaded to facilitate desiredcoupling with respective bone screws 10 or other fasteners.

Each of sleeves 350 a-c comprises a tab-tabs 360 a-c,respectively—configured to facilitate fixed engagement between thesleeves and base portion 310. In the depicted embodiment, each of tabs360 a-c is configured to extend over and engage a part of base portion310 that defines opening 322.

As shown in FIG. 3, tabs 360 a-c may comprise hook-shaped ends tofurther facilitate engagement with base portion 310. In addition, insome embodiments, a corresponding recess, depression, and/or matingfeature may be formed on base portion 310 to provide for a more secureengagement. Tabs 360 a-c may also be flexible to allow them to flex awayfrom and then resiliency flex towards base portion 310. Tabs 360 a-c mayalso be formed from the same surface/material defining the holes formedin sleeves 350 a-c.

More particularly, in the depicted embodiment, tabs 360 a-c may, liketabs 160 of implant 100, be respectively defined by two parallel slitsformed within sleeves 350 a-c. This allows tabs 360 a-c to flex into andaway from sleeve recesses 315 a-c, which may allow for hook-shapedportions formed on the ends of tabs 360 a-c to flex away from andresiliency engage base portion 310.

Each of the various sleeves 350 a-c may further comprise a correspondingrim 355 a-c. These rims 355 may be sized so as to prevent the sleeves350 from passing all the way through sleeve recesses 315 a-c. Inaddition, the interior of sleeves 350 a-c and/or the heads of screws 10may be dimensioned so as to prevent the screws from passing through oneor more portions of sleeves 350 a-c.

FIG. 5 depicts another embodiment of a stand-alone ALIF implant 500.Implant 500 comprises a base portion 510 and a secondary fastenerportion 550. Again, base portion 510 and secondary portion 550preferably comprise different materials such that implant 500 may takeadvantage of the different characteristics of the two differentmaterials in the same implant. For example, in some embodiments, baseportion 510 may comprise a silicon nitride ceramic material or anothersimilar ceramic material, and secondary fastener portion 550 maycomprise other materials more suitable for engaging a threaded fastener,such as titanium metals, titanium alloys, or other metals.

Base portion 510 of implant 500 comprises an upper surface 502, a lowersurface 504, a first side wall surface 506, a second side wall surface508 opposite from surface 506, a front end wall surface 512, and a rearend wall surface 514 opposite from front end wall surface 512.

Upper and lower surfaces 502 and 504 may both comprise a plurality ofengagement structures or teeth 520. Teeth 520 may be arranged inparallel rows that may each extend at least substantially perpendicularto the direction in which side wall surfaces 506 and 508 extend. Uppersurface 502 also comprises an opening 522 that also extends throughlower surface 504 to allow for ingrowth of bony material therethrough.

In the embodiment of FIG. 5, secondary fastener portion 550 comprises aplate configured to fit over and engage with front end wall surface 512and further configured to receive fasteners, such as bone screws,therethrough. Plate 550 comprises three fastener openings, namely,fastener openings 552, 554, and 556. Each of these fastener openings maybe configured to receive a bone screw 10 or another such fastener.Fastener openings 552, 554, and 556 may be threaded in some embodiments.

Fastener openings 552, 554, and 556 extend from a front surface 557 ofsecondary portion 550 such that implant 500 comprises a front end wailsurface defined in whole by front end wall surface 557 of secondaryportion 550. Secondary portion 550 further comprises two opposingflanges 559 and 561 that may be configured to be received incorresponding depressions 507 and 509 formed in side wall surfaces 506and 508 of base portion 510. In some embodiments, lips or hookstructures may be formed at the end of flanges 559 and 561 to furtherfacilitate a secure coupling between base portion 510 and secondaryfastener portion 550.

As also shown in FIG. 5, a shelf 521 may be formed on base portion 510,which may further facilitate desired coupling between base portion 510and secondary fastener portion 550. Shelf 521 may extend from the distalsurface of front end wall surface 512, and may be configured to engage acorresponding structure, such as shelf 571, on secondary fastenerportion 550 In some embodiments, shelves 521 and 571 may be configuredto engage in a nesting fashion and may therefore have shapes suitablefor such engagement. In some embodiments, additional shelves may beformed adjacent to lower surface 504 if desired. In still otherembodiments, flanges 559 and 561 may not extend the entire distancebetween upper surface 502 and lower surface 504, and depressions 507/509may similarly not extend this entire distance such that flanges 559 and561 are prevented from moving up and/or down with respect to baseportion 510 by virtue of a “roof” and a “floor” to depressions 507/509.This may be done as an alternative to, or in addition to, providing theshelves referenced above.

Implant 500 further comprises slots 570 formed within the front surfaceof secondary fastener portion 550. Although only one slot 570 isdepicted in FIG. 5, it should be understood that another similar slot570 may also be formed on the opposite side of secondary fastenerportion 550. These slots 570 may be configured to be engaged withcorresponding tabs, protrusions, or other engagement structures formedon an inserter or other instrument, which may be used to squeeze and/orgrip implant 500.

FIG. 6 depicts still another embodiment of a stand-alone ALIF implant600. Implant 600 is similar to implant 500 with a few exceptions. Forexample implant 600 is configured to receive four bone screws 10, two ofwhich are configured to extend through the upper surface 602 and two ofwhich are configured to extend through the lower surface 604. Inaddition, although, like implant 500, implant 600 comprises a separatefastener opening for each fastener, namely, fastener openings 652, 654,656. and 658. Two of these fastener openings overlap In particular,fastener openings 656 and 658 overlap but extend through two separatepartial fastener openings or recesses formed in base portion 610,namely, fastener openings 626 and 628, respectively. In otherembodiments, fastener openings 626 and 628 may be combined into a singlerecess or opening configured to receive two or more separate fasteners.

In most other respects, implant 600 is similar to implant 500. Thus,implant 600 comprises a base portion 610 and a secondary fastenerportion 650 comprising a plate Base portion 610 comprises an uppersurface 602, a lower surface 604, a first side wall surface 606, asecond side wall surface 608 opposite from surface 606, a front end wallsurface 612, and a rear end wall surface 614 opposite from front endwall surface 612.

Similarly, upper and lower surfaces 602 and 604 both comprise aplurality of engagement structures or teeth 620, which may be arrangedin parallel rows that may each extend at least substantiallyperpendicular to the direction in which side wall surfaces 606 and 608extend. Upper surface 602 also comprises an opening 622 that alsoextends through lower surface 604 to allow for ingrowth of bony materialtherethrough.

Secondary portion 650 further comprises two opposing flanges 659 and 661that may be configured to be received in corresponding depressions 607and 609 formed in side wall surfaces 606 and 608 of base portion 610.However, unlike implant 500, implant 600 lacks corresponding shelfstructures to further facilitate coupling between base portion 610 andsecondary portion 650. Given a sufficiently-tight engagement betweenflanges 659/661 and depressions 607/609, such features may beunnecessary for certain applications and embodiments.

FIGS. 7-9 depict yet another embodiment of a stand-alone ALIF implant700. Implant 700 is configured to receive four bone screws (notillustrated), two of which are configured to extend through the uppersurface 702 and two of which are configured to extend through the lowersurface 704. Like implant 600, implant 700 comprises a separate fasteneropening for each fastener, namely, fastener openings 752, 754, 756, and758, and two of these fastener openings overlap. More particularly,fastener openings 756 and 758 overlap.

One or more of fastener openings 752, 754, 756 and 758 may comprise oneor more anti-backout features configured to prevent or at least inhibitscrews or other fasteners from being removed from these fasteneropenings once fully positioned therein. For example, as best seen inFIGS. 7 and 8, fastener openings 752 and 754 comprise a plurality ofconcentrically-positioned protrusions 743. Such protrusions 743 may beconfigured to engage with corresponding divots, slots, or otherrecessions formed on a bone screw or other fastener, as discussed ingreater detail below. Although not visible is FIG. 7, fastener openings756 and 758 may also comprise such protrusions if desired.

In alternative embodiment protrusions 743 may be replaced withsimilarly-positioned divots, slots, or recessions, and the bonecrews/fastener may instead be formed with protrusions. In this manner,the screws/fasteners may be configured to automatically lock into placeat a desired location with the various fastener openings. In someembodiments, this locking may be configured to be audible to allow asurgeon to audibly confirm that the bone screws/fasteners have beenadequately locked into place within an implant. As also discussed ingreater detail below, in some embodiments, the protrusions andrecessions may be configured an arranged so as to only allow forprogression of a screw/fastener in one direction prohibit or at leastinhibit reverse threading opposite direction. In other words, in someembodiments, the protrusions an recessions may be configured andarranged to allow for a protrusion to exit from one recession and enteran adjacent recession when the screw is advancing into a screw hole, butinhibit/prohibit a protrusion from exiting a current recession oppositedirection.

Unlike implant 600, base portion 710 of implant 100 lacks front end wallsurface. Instead the front end wall surface 712 of implant 700 is whollydefined by secondary fastener portion 50. Base portion 710, however,comprises an upper surface 702, a lower surface 704, a first side wallsurface 706, a second side wall surface 708 opposite from surface 706,and a rear end wall surface 714.

Like many of the embodiments discussed previously, upper and lowersurfaces 702 and 704 both comprise a plurality of engagement structuresor teeth 720, which may be arranged in parallel rows that may eachextend at least substantially perpendicular to the direction in whichside wall surfaces 706 and 708 extend. Upper surface 702 also comprisesan opening 722 that also extends through lower surface 704 to allow foringrowth of bony material therethrough.

Secondary portion 750 further comprises two opposing flanges 759 and 761that may be configured to be received in corresponding depressions 707and 709 formed in side wall surfaces 706 and 708 of base portion 710.However, unlike implant 600, implant 700 comprises two opposing lockingmember openings 780 and 782 positioned along a side of secondaryfastener portion 750 opposite from front end wall surface 712. Lockingmember openings 780 and 782 are configured to receive locking members783, which in the depicted embodiment comprise locking pins. As bestseen in FIG. 9, locking member openings 780 and 782 may comprise slits784 and 785, respectively, which may allow for some of the materialdefining locking member openings 780 and 782 to flex upon receiving alocking pin 783 therein. This may allow for locking pins 783 to create afriction fit, snap fit, or otherwise secure base portion 710 in placerelative to secondary fastener portion 750, as discussed in greaterdetail below.

Locking member openings 780 and 782 may be positioned adjacent torespective recesses formed within secondary fastener portion 750. Inparticular, secondary fastener portion 750 may comprise a first recess786 positioned adjacent to locking member opening 780 and a secondrecess 788 positioned adjacent to locking member opening 782. Recesses786 and 788 may be defined in part by flanges 759 and 761, respectively,as shown in FIGS. 7-9.

Recesses 786 and 788 may be configured to receive at least a portion ofthe ends of opposing side wails of base portion 710. In someembodiments, an end portion of these side walls may form an enlargedtip, as best seen in FIG. 9. Recesses 786 and 788 may similarly beformed to have a smaller diameter opening and then expand to accommodatethis enlarged tip as also best seen in FIG. 9. Recesses 786 and 788 maytherefore accommodate the side wall tips, or another similar portion ofbase portion 710, in a puzzle-piece or nesting fashion. In some suchembodiments, the distal tips of the side walls may be prevented orinhibited from being inserted in recesses 786 and 788 in a horizontaldirection (within a plane parallel to upper and/or lower surfaces 702and 704). In other words, secondary fastener portion 750 may be coupledwith base portion 710 by approximating these pieces once positionedvertically or on top of one another.

Alternatively, if slits 784 and 785 are sufficiently wide and/orrecesses 786 and 788 are dimensioned appropriately, some embodiments mayallow for such coupling in a horizontal direction (or within the sameplate). For example, in some embodiments recesses 786 and 788 may beconfigured to flex open, due to the presence of slits 784 and 785, toaccommodate the side wall tips, another similar portion of base portion710, and then flex back into position prevent these side wall tips frombeing removed from recesses 786 and 788. These components may then belocked into place by inserting pins 783 or another similar lockingmember into locking member openings 780 and 752. Pins 783 may beconfigured to be received in locking member openings 780/782 in afriction-fit manner. Alternatively, pins 783 and/or locking memberopenings 780/782 may be threaded to facilitate such securement.

It is expected that a variety of alternative embodiments will beapparent to those of ordinary skill in the art after receiving thebenefit of this disclosure. For example, alternative embodiments arecontemplated in which various elements or components disclosed as formedon a base portion may instead be formed on a secondary portion, and viceversa. For example, in some embodiments, locking member openings may beformed in base portion 710 instead of secondary portion 750. Similarly,recesses 786 and 788 may be formed in base portion 710 rather thansecondary portion 750.

FIGS. 10 and 11 depict yet another embodiment of a stand-alone ALIFimplant 1000 comprising a base portion 1010 and a secondary fastenerportion 1050. Implant 1000 differs from the previously-discussedembodiments in that secondary fastener portion 1050 comprises twoopposing recesses 1086 and 1088 that comprise locking member openings1080 and 1082 configured to receive a pin 1083 or other locking membertherethrough. In the depicted embodiment, recesses 1086 and 1088comprise slits. However, other embodiments are contemplated in whichrecesses 1086 and 1088 may instead comprise holes formed in secondaryfastener portion 1050.

Locking member openings 1080 and 1082 are further configured to bealigned with corresponding locking member openings 1090 and 1092 formedwithin and extending through tips 1094 and 1095 of side walls 1006 and1008 of base portion 1010. Tips 1094 and 1095 are narrowed relative tothe distance between upper surface 1002 and lower surface 1004 so as toallow for being positioned within recesses 1086 and 1088 without makingthe upper and lower surfaces of secondary fastener portion 1050 extend agreater distance than upper surface 1002 and lower surface 1004.

Once base portion 1010 is properly positioned relative to secondaryfastener portion 1050, pins 1083 may be secured through locking memberopenings 1080 and 1082, and locking member openings 1090 and 1092 toensure a secure coupling between base portion 1010 and secondaryfastener portion 1050. Pins 1083 may be so secured by a friction fit,for example, or may be threaded. Stand-alone ALIF implant 1000 isotherwise similar to stand-alone ALIF implant 700.

FIG. 12 depicts an example of a bone screw 1230 configured for use inconnection with one or more of the spinal implants disclosed herein.Bone screw 1230 comprises an unthreaded head 1232 and a threaded section1234. In the depicted embodiment, threaded section 1234 comprises avariable-pitch thread that comprises threads that are progressivelycloser together towards unthreaded head 1232. In some embodiments,threaded section 1234 may comprise a variable-pitch thread over theentire length of the threaded section 1234. Alternatively, threadedsection 1234 may comprise multiple sub-sections, one or more of whichhave a constant pitch and one or more of which (preferably near the head1232) are variable pitch. As another alternative, multiple leads may beused instead of using a single lead with variable pitch. In any event,such variable-pitch, multiple leads, and/or sectioned threads may beuseful in creating compression between an intervertebral device andpatient bone, which may enhance the anti-backout characteristics of theimplant.

Head 1232 may comprise a tapered surface, which may be used to preventbone screw 1230 from passing all of the way through a correspondingfastener opening in an implant. In some embodiments, head 1232 maytherefore taper from a minimum diameter less than a major diameter ofthe threads of threaded section 1234 to a maximum diameter greater thana major diameter of these threads.

Bone screw 1230 further comprises a plurality of recessions 1235positioned about a proximal portion of threaded section 1234. Aspreviously mentioned, recessions 1235 may be configured to engagecorresponding protrusions formed within a fastener opening of a spinalimplant or other biomedical implant. In alternative embodiments,recessions 1235 may be positioned about an unthreaded section of bonescrew 1230. For example, in some embodiments, recessions 1235 may bepositioned about unthreaded head 1232 rather than about a proximalportion of threaded section 1234.

FIG. 13 depicts a close-up view of a fastener opening 1252 of a spinalimplant 1200. One or more other similar openings (not shown in thisfigure) may also be included if desired. As shown in FIG. 13, fasteneropening 1252 comprises a plurality of protrusions 1243 positioned alonga surface defining fastener opening 1252. Protrusions 1243 may bedefined by a two opposing ramped surfaces, namely, ramped surfaces 1245a and 1245 b. Ramped surfaces 1245 a and 1245 b may both lead to acentral portion 1246 of protrusion 1243. In some embodiments, centralportion 1246 may comprise a flat surface, or an at least substantiallyflat surface. In some embodiments, ramped surfaces 1245 a and 1245 b maycomprise concave surfaces. Alternatively, ramped surfaces 1245 a and1245 b may comprise flat surfaces positioned at an angle with respect tocentral portion 1246 so as to facilitate desired positioning ofprotrusions 1243 within respective recessions, such as recessions 1235,of a bone screw or other fastener.

In some preferred embodiments, protrusions 1243 may be arranged in ahelical pattern about a surface defining fastener opening 1252, as shownin FIG. 13. This helical pattern may be configured to match, or at leastsubstantially match, a corresponding helical pattern of threads of abone screw, such as bone screw 1230. Although some embodiments arecontemplated in which recessions 1235 may similarly be placed about bonescrew 1230 in a helical pattern, in certain preferred embodimentsrecessions 1235 are not placed in a helical pattern. Instead, recessions1235 may be placed in a circular pattern about the same portion (i.e.,same position along the axis of bone screw 1230) of bone screw 1230.

In addition, in some preferred embodiments, protrusions 1243 may beconfigured to taper, again, to match the taper of a screw, according totheir positioning depth within fastener opening 1252. More particularly,in certain preferred embodiments, the height of protrusions 1243(measured from the wall defining fastener opening 1252) may increasefrom the proximal portion of a particular fastener opening 1252 to thedistal portion of the fastener opening 1252. In some embodiments, thistaper of the helical protrusions may be configured to match, or at leastsubstantially match, the taper of a minor diameter of an associatedscrew, such as bone screw 1230. In this manner, bone screw 1230, oranother similar fastener, may be configured to allow for rotation ofbone screw 1230 within fastener opening 1252 once at least one ofprotrusions 1243 has engaged a corresponding recession 1235 in aparticular direction, but prevent, or at least inhibit, rotation of bonescrew 1230 in an opposite direction. This may be used to prevent, or atleast inhibit, unwanted backout of bone screw 1230.

In some embodiments, one or more (in some cases, all) of protrusions1243 may comprise a width (measured in a direction perpendicular to, orat least substantially perpendicular to, the direction in which rampedsurfaces 1245 a and 1245 b extend and/or parallel to, or at leastsubstantially parallel to, the direction in which bone screw 1230extends into a fastener opening 1252) that is less than a pitch of bonescrew 1230 (or at least a particular pitch of bone screw 1230 in theregion in which recessions 1235 are positioned).

However, it may be preferable, depending upon the positioning ofrecessions 1235, to create recessions 1235 such that they comprise aheight (measured along the axis of bone screw 1230) that issubstantially greater than the width (as described above) of protrusions1243. This may allow for multiple protrusions 1243 to be simultaneouslypositioned within multiple respective recessions 1235. In someembodiments, one or more (in some cases, all) of the recessions 1235 maycomprise a height that is no greater than twice the pitch of the threadsat or near the location of the recessions 1235. In some embodiments, therecessions 1235 may be configured and positioned so as to avoid crossingmore than one thread crest. However, other embodiments are contemplatedin which the height may be greater than this length, particularly if therecessions extend beyond the extent of the threads, such as on ortowards the unthreaded head 1232 of the bone screw 1230.

Although, as mentioned above, in certain preferred embodiments,protrusions 1243 may be arranged in a tapered and/or helical mannerabout fastener opening(s) 1252, in some embodiments, each of theprotrusions 1243 may themselves not be arranged in this manner. In otherwords, the protrusions 1243 may be positioned to extend parallel to, orat least substantially parallel to a perimeter of fastener openings(s)1252 such that each individual protrusion 1243 does not itself taperinwardly, despite the fact that the placement of the protrusions 1243results in a collective taper inwardly within a particular fasteneropening 1252. This may be useful in order to further facilitate adesired anti-backout effect by creating an interference fit between oneor more of the protrusions 1243 and one or more respective recessions1235.

It is contemplated that, in some alternative embodiments, theprotrusions may instead be positioned on a bone screw or other fastenerand the recessions may be positioned about a fastener opening. However,it is thought that the preferred embodiments disclosed herein whereinthe protrusions are positioned in a tapered helical manner aboutfastener opening(s) 1252 and recessions are positioned about a proximalport on of bone screw(s) 1230 may be preferred to certain applications.

FIG. 14 depicts an embodiment of an inserter tool 1400 that may be usedto insert one or more of the implants disclosed herein and/or installscrews and/or fasteners into one or more of the implants disclosedherein. Inserter 1400 comprises a handle 1410, a shaft 1420, and a tip1430. Handle 1410 comprises a lever 1412 configured to lock tip 1430 inplace. In some embodiments, tip 1430 may be replaced by a variety ofother tips having different shapes and sizes such that a single inserter1400 may be used in connection with an entire collection of standaloneALF implants or other spinal implants. Thus lever 1412 may be configuredsuch that in one position, tip 1430 is secured in place and in a secondposition, lever 1412 releases tip 1430 to for a different tip to be usedwith tool 1400.

Tip 1430 comprises two fastener holes, namely fastener hole 1432 andfastener hole 1434. Hole 1432 is configured to be coupled withcorresponding fastener opening of a spinal implant to facilitateplacement of bone screws or other fasteners within the fastener opening.Similarly, hole 1434 is configured to be coupled with anothercorresponding fastener opening of the same spinal implant to facilitateplacement of bone screws or other fasteners within the fastener opening.As illustrated in FIG. 14, hole 1432 is positioned on one side ofinserter 1400 and hole 1434 is positioned on an opposite side ofinserter 1400. Holes 1432 and 1434 are also angled in oppositedirections such that hole 1432 can be aligned and coupled with afastener opening configured to deliver a bone screw into a firstvertebral bone and hole 1434 can be aligned and coupled with a fasteneropening configured to deliver a second bone screw into a secondvertebral bone, as described above in connection with variousembodiments of standalone ALIF implants. Holes 1432 and 1434 may befurther configured to be coupled with (in some embodiments, fixedlyengage) a guide tube configured to deliver the bone screws or otherfasteners through holes 1432 and 1434 and, ultimately, into fasteneropenings of a spinal implant as described in greater detail below.

Of course, a wide variety of alternative tips are contemplated havingvarying numbers, angles, and positions for the fastener holes. Forexample, FIG. 15 illustrates a close-up view of a tip 1530 of analternative embodiment of an inserter tool 1500. Tip 1530 comprises twoadjacent fastener holes 1532 and 1534, both of which are positioned onthe same side of inserter 1500 and both of which are angled in the samemanner so as to be angled towards the same vertebral body duringsurgery. In some embodiments, another two fastener holes (not shown inFIG. 15) may be positioned on the opposite side so as to facilitatedelivery of bone screws or other fasteners into a different vertebralbody. Such an embodiment may be used, for example in connection withstand-alone ALIF implant 600 of FIG. 6.

Fastener holes 1532 an 1534 further comprise locking features configuredto facilitate a secure connection between inserter 1500 and one or morecorresponding guide tubes (discussed in greater detail below). Moreparticularly, fastener 1532 and 1534 both comprise an internal channel1533 positioned in between the top and bottom peripheral openingsdefining holes 1532 and 1534. Holes 1532 and 1534 further comprise aplurality of slots 1535 defined within the holes such that channel 1533is exposed only in the areas of holes 1532 and 1534 where slots 1535 arepositioned. This may allow for a guide tube having a similar pluralityof tabs positioned on an exterior surface to be locked into position byaligning the tabs with the slots 1535 and then rotating the guide tube,as discussed in greater detail below.

Of course, a variety of alternative embodiments are contemplated. Forexample although fastener holes 1532 and 1534 are shown as having threeslots 1535 positioned evenly about these holes, other numbers andpositions of such slots 1535 may be used as desired. In addition, in aspecific alternative configuration for facilitating a secure couplingbetween a guide tube and an inserter instrument, the guide tube may lackslots 1535. In such embodiments, the guide tube may comprise a singletab or ridge, or multiple tabs/ridges, and may be configured with one ormore slits in the end of the guide tube (in some embodiments, two slitspositioned 180 degrees from each other). This may allow the tube to becontracted and fit within a fastener hole of an inserter tool and thenexpanded with the fastener hole such that the tab(s) can enter thechannel.

FIG. 16 depicts a distal end of an embodiment of a guide tube 1600 thatmay be used to install one or more of the implants described herein andmay also be used in connection with one or more of the inserter toolsdescribed herein. Guide tube 1600 comprises a lumen 1605 defined by ashaft comprising a distal portion 1620 that is angled with respect to aprimary portion 1610 of the guide tube 1600 shaft. In some embodiments,the angle with which distal portion 1620 extends relative to primaryportion 1610 may at least substantially correspond with an angle that afastener opening of a spinal implant extends relative to an axis of theimplant, such as an axis defined by the top and/or bottom surface of theimplant. However in other embodiments, this need not be the case.

For example, in some embodiments, the angle with which distal portion1620 extends relative to primary portion 1610 may be greater than theangle of angle that a fastener opening of a spinal implant extendsrelative to an axis of the implant. This may be useful to allow forproviding a greater degree of clearance between guide tube 1600 andinserter 1500 to prevent the two instruments from interfering with oneanother during a surgical procedure. In some embodiments, this angle mayresult in a projection of the axis of guide tube 1600 crossing aprojection of the axis of inserter 1500 such that the proximal portionof guide tube 1600 extends away from the proximal portion of inserter1500 to allow for additional room between the instruments at therespective proximal ends.

Guide tube 1600 further comprises a hood 1625 positioned along at leasta portion of the distal portion 1620 of guide tube 1600. Hood 1625 maybe used to cover an expanded region 1608 of the lumen 1605 of guide tube1600. Expanded region 1608 may be provided to allow for one or more bonescrews or other fasteners to extend through the angled distal portion1620 of guide tube 1600. Hood 1625 may be used to prevent the screwsfrom exiting guide tube 1600 in this region. Hood 1625 is substantiallycoincident with angled distal portion 1620 of the shaft of guide tube1600 in the depicted embodiment. However, other embodiments arecontemplated in which hood 1625 is positioned along less of angleddistal portion 1620. This variable may depend upon the angle betweendistal portion 1620 and primary portion 1610. In the depictedembodiment, hood 1625 completely encloses expanded region 1608. However,other embodiments are contemplated in which hood 1625 only partiallyencloses expanded region 1608.

Guide tube 1600 further comprises a tip 1630 comprising a plurality oftabs 1635 corresponding with the plurality of slots 1535 positionedwithin fastener holes 1532 and 1534 of inserter tool 1500. Guide tube1600 may be coupled with a particular fastener hole by aligning tabs1635 with slots 1535, approximating guide tube 1600 with inserter tool1500 to insert tabs 1635 into slots 1535, and then rotating guide tube1600 with respect to inserter tool 1500 to allow tabs 1635 to enterchannel 1533 and lock guide tube 1600 in place.

In alternative embodiments, guide tube 1600 may be snap-fit into place.For example, in some embodiments, tabs 1635 may instead comprise asingle tab or protrusion, which may extend all of the way around aperimeter of tip 1630. Such embodiments may comprise one or more slitspositioned in the end of tip 1630, which may allow the distal end of theguide tube to flex and fit within a fastener hole of an inserter tool,such as fastener holes 1532 and 1534 of inserter tool 1500, after whichthe guide tube may be expanded within the fastener hole such that thetab/protrusion can enter channel 1533 without requiring a particularrotational orientation. In some preferred embodiments, tip 1630 maycomprise two such slits positioned opposite (at or about 180 degrees)from one another.

FIG. 17 depicts a perspective view of the entire guide tube 1600. Asshown in this figure, guide tube 1600 further comprises a handle 1640.Handle 1640 comprises a collar 1642 that may be used to repositionhandle 1640 with respect to the shaft of guide tube 1600. Moreparticularly, a user may pull back on collar 1642, rotate handle 1640 toa desired position relative to the shaft of guide tube 1600, and thenrelease collar 1642 to lock handle 1640 in place. Collar 1642 is coupledto a handle hub 1644, which may comprise elements used to allow for suchrepositioning, such as a ratchet mechanism, a ball joint, a clutchmechanism, or the like.

It can also be seen in FIG. 17 that handle 1640 initially extends at anat least substantially perpendicular angle relative to the shaft ofguide tube 1600 and then angles upward slightly relative to thisperpendicular direction. This may provide for a more ergonomic feel forguide tube 1600. In some embodiments, this angle, like the rotationalposition of handle 1640, may also be adjustable.

In some embodiments, guide tube 1600 may be configured to be directlycoupled with an implant without use of an inserter. For example in someembodiments, the implant fastener openings may be configured to directlyreceive the distal end of a guide tube by way of a friction fit, or oneof the other locking coupling features disclosed above relative to theinserter 1500, such as slots 1535 and tabs 1635, for example. In stillother embodiments, the guide tube may comprise multiple lumens eachconfigured to engage with a separate opening, either of an inserter toolor an implant directly, and drive a separate fastener therethrough,either simultaneously or sequentially. In some such embodiments, asingle lumen at a proximal end of the guide tube may split into multiplelumens at the distal end.

Some embodiments may be configured to have one or more screws/fastenerspre-loaded within one or more of the guide tube lumens. For example, insome embodiments, one or more resiliency deformable features may beformed adjacent to a distal opening of the guide tube. Such features maybe used to keep the pre-loaded screws/fasteners in the guide tube untilsufficient force, such as may be provided by a driver tool, is used todeform these components to allow them to fully pass through the distalopening of the guide tube.

In some embodiments, the guide tube may be directly coupled with only asubset (rather than all, as discussed above) of the fastener openings ofan implant or inserter. Thus, for example, a subset of fastener openingsof an implant may be more difficult to access. Such fastener opening(s)may have a direct and/or permanent coupling with a guide tube or theguide tube may have a direct and/or permanent coupling with an inserter.Other fastener openings that are more easily accessible may then beaccessed by a different guide tube.

FIG. 18 depicts an embodiment of a driver 1800 that may be used toinstall one or more of the implants described herein and may also beused in connection with one or more of the inserter tools and/or guidetubes described herein during such procedures. Driver 1800 comprises ashaft 1810 a proximal tip 1820, and a distal tip 1830. Shaft 1810comprises a relatively rigid section 1812 and a flexible section 1814.Flexible section 1814 is configured to allow for shaft 1810 to flexwithin guide tube 1600. More particularly, in the depicted embodiment,flexible section 1814 is specifically configured to allow for flexing ofshaft 1810 within the region of distal portion 1620 of guide tube 1600.Thus, in some preferred embodiments, flexible section 1814 may have alength that is at least substantially equal to a length of an angledportion of a guide tube (such as distal portion 1620 of guide tube1600).

In the depicted embodiment, flexible section 1814 is created by cuttinga series of cuts, such as laser cuts for example, that may extendcircumferentially around the outer surface of the flexible section 1814to enhance flexibility. In some embodiments, the cuts may score theouter surface or flexible section 1814. Alternatively, the cuts mayextend all of the way through a wall of flexible section 1814 to ahollow interior. In such embodiments, the cuts may form discreteportions that may interlock due to the shape of the cuts. In thedepicted embodiment, for example, the cuts may be formed in the shape ofinterlocking puzzle pieces.

Proximal tip 1820 comprises a keyed section 1822 configured to engage atool for providing a torsional force to driver 1800 to drive bone screwsor other fasteners through an implant and, in some embodiments, into apatient's bone, such as into vertebral bodies of a patient's spine.Distal tip 1830 similarly comprises a keyed section 1832 configured toengage a bone screw or other fastener. Adjacent to keyed section 1832,distal tip 1830 further comprises an expanded region 1834. Expandedregion 1834 may be used to keep driver 1800 centered within guide tube1600, which may help keep a desired trajectory for bone screws or otherfasteners being driven within guide tube 1600. In the depictedembodiment, expanded region 1834 comprises a bulb. However, otherembodiments are contemplated in which expanded region 1834 insteadcomprises one or more protrusions configured to engage an inside wall ofthe lumen of guide tube 1600.

In some embodiments, two or more of the instruments disclosed herein maybe combined into a single instrument. For example, the driver may becoupled with the guide tube in such a way that a single instrument isused for both functions, as described in greater detail below.Similarly, in some embodiments, the guide tube and inserter may becombined into a single instrument. Alternatively, the driver, guidetube, and inserter may all three be combined into a single instrument.

An example of one such combined instrument is shown in the phantom,perspective view of FIG. 19, which depicts an embodiment of a surgicalinstrument 1900 comprising a combined guide tube and flexible driver.

Instrument 1900 comprises a guide tube 1910 and a flexible driver 1950positioned within the guide tube 1910. In the depicted embodiment,flexible driver 1950 is positioned within guide tube 1910 such thatflexible driver 1950 cannot be fully withdrawn from guide tube 1910, andsuch that guide tube 1910 and flexible driver 1950 are components of asingle instrument, rather than separate instruments that may be usedtogether.

This may be accomplished in a number ways, as those of ordinary skill inthe art will appreciate. However, in the depicted embodiment, this isaccomplished by providing one or more collars or other expanded regions,such as collar 1955, that are positioned on selected portions of thedriver 1950. Collar 1955 may be configured to engage a correspondingshelf, such as shelf 1915, on guide tube 1910, so as to confine driver1950 within guide tube 1910. A similar shelf or other retention featuremay be positioned at an opposite end of the guide tube to engage anothercollar or other such retention feature on the driver if desired toretain the driver within a particular region of the guide tube. However,as discussed above, other embodiments are contemplated in which thesecomponents are instead separate instruments that may be used together incertain implementations of inventive methods disclosed herein.

Surgical instrument 1900 further comprises a spring 1980. Spring 1980,or another similar means for spring loading driver 1950 with respect toguide tube 1910, may be used to bias driver 1950 in a particulardirection relative to guide tube 1910. For example, in the depictedembodiment, spring 1950 biases driver 1950 towards the position depictedin FIG. 20, which depicts instrument 1900 in a retracted position with abone screw 10 retracted into the guide tube 1910 portion of the combinedinstrument 1900.

Bone screw 10, or another such fastener, may be coupled with a distalend of driver 1950 by way of a tapered “stick-fit” on the driver tip1952 or some other retention feature or features. Thus, in use, driver1950 may be advanced distally relative to guide tube 1910 such thatdriver tip 1952 extends out of the distal opening of guide tube 1910. Insome embodiments, driver tip 1952 may comprises a keyed sectionconfigured to facilitate engagement with a bone screw or other fastener,as previously discussed. After being coupled with a bone screw or otherfastener, driver 1950 may be retracted relative to guide tube 1910 suchthat driver tip 1952 and/or bone screw 10 are at least partially (insome cases, fully) retracted within a lumen of guide tube 1910. Once thedistal end of guide tube 1910 has been coupled with a fastener openingof an implant, such as a stand-alone anterior lumbar interbody fusionspinal implant, driver 1950 may be used to advance (in some cases, byrotation of driver 1950) bone screw into the fastener opening and,ultimately, into a vertebral body of a patient's spine.

In some embodiments, one or more bone screws or other fasteners may bepre-loaded within the lumen of guide tube 1910. For example, in someembodiments, one or more resiliently deformable features may be formedadjacent to a distal opening of guide tube 1910. Such features may beused to keep the pre-loaded bone screw 10 in the guide tube untilsufficient force is used to deform these components to allow bone screw10 to fully pass through the distal opening of guide tube 1910.Preferably, the features/components used to keep bone screw 10 withinguide tube 1910 are sufficient to prevent the force of spring 1980 alonefrom advancing bone screw 10 out of guide tube 1910.

As also previously described, driver 1950 may comprise a flexiblesection 1954, which may be used to facilitate advancement of a bonescrew or other fastener though an angled portion 1914 of guide tube1910. Driver 1950 may further comprise a proximal tip 1956, which, asdescribed above, may comprise a keyed section configured to engage atool for providing a torsional force to driver 1950 to drive bone screwsor other fasteners through an implant and, in some embodiments, into apatient's vertebrae or other bone structure. In some embodiments,instrument 1900 may comprise a drill or awl to further facilitate suchdriving of bone screws.

In the retracted position illustrated in FIG. 20, bone screw 10 may beat least partially contained within angled portion 1914 of guide tube1910. As previously discussed, guide tube 1910 may comprise a hood 1925positioned along at least a portion of guide tube 1910. Hood 1925 may beused to cover an expanded region 1908 of a lumen of guide tube 1910,which may allow bone screw 10 to extend through the angled portion 1914of guide tube 1910.

FIG. 21 depicts yet another embodiment of a stand-alone ALIF implant2100. Implant 2100 comprises a base portion 2110 and a secondaryfastener portion 2150. In preferred embodiments, base portion 2110 andsecondary portion 2150 comprise different materials such that implant2100 may take advantage of the different characteristics of the twodifferent materials in the same implant. For example, in someembodiments, base portion 2110 may comprise a silicon nitride ceramicmaterial, another similar ceramic material, or another material that isnot readily subject to receiving stable threads for use in fixation tovertebral bones without damaging the implant, and secondary fastenerportion 2150 may comprise other materials more suitable for beingthreaded and/or engaging a threaded fastener, such as titanium metals,titanium alloys, or other metals.

Base portion 2110 of implant 2100 comprises an upper surface 2102, alower surface 2104, a first sidewall 2106, a second sidewall 2108opposite from sidewall 2106, and a rear end wall 2114. Unlike severalembodiments previously discussed, implant 2100 lacks a front end wall.Instead, secondary portion 2150 bridges a gap between a first end offirst sidewall 2106 and a corresponding first end of second sidewall2108 so as to wholly define a second or front end wall of implant 2100opposite from rear end wall 2114. In addition, base portion 2110 atleast substantially comprises a “C” shape.

Upper and lower surfaces 2102 and 2104 may both comprise a plurality ofengagement structures or teeth 2120. Teeth 2120 may be arranged inparallel rows that may each extend at least substantially perpendicularto the direction in which side walls 2106 and 2108 extend. Upper andlower surfaces 2102 and 2104 are also both defined in part by baseportion 2110 and in part by secondary portion 2150.

Similarly, an opening is defined in part by base portion 2110 and inpart by secondary portion 2150 when base portion 2110 has been coupledwith secondary portion 2150. This opening may allow for ingrowth of bonymaterial therethrough.

In the embodiment of FIG. 21, secondary portion 2150 is configured to becoupled with base portion 2110 by way of two locking members, namelylocking member 2107 and locking member 2109. These locking members maycomprise, for example, screws, bolts, pins, or the like. In the depictedembodiment, locking members 2107 and 2109 are threaded, and are receivedin corresponding threaded openings 2190 and 2192 formed within sidewalls2106 and 2108, respectively.

In some embodiments, a recess 2105 may be formed within opposite ends ofsecondary portion 2150 such that no portion of the respective lockingmembers 2107/2109 extends outside of a plane defined by a front surfaceof secondary portion 2150, as illustrated in FIG. 21. Openings 2101 mayextend through such recesses 2105 (only one is visible in FIG. 21) onopposite ends of secondary fastener portion 2150 such that the head oflocking members 2107 and 2109 sit within these recesses 2105 followingassembly. Locking members 2107 and 2109 extend through openings 2101 andinto respective openings 2190 and 2192 formed within opposing sidewallsof base portion 2110.

Secondary portion 2150 is further configured to receive fasteners, suchas bone screws, therethrough. More particularly, secondary portion 2150comprises four fastener openings, namely, fastener openings 2152, 2154,2156, and 2158. Each of these fastener openings may be configured toreceive a bone screw (not shown in the figure) or another such fastenertherethrough. Fastener openings 2152, 2154, 2156, and 2158 may bethreaded in some embodiments.

FIGS. 22A and 22B depict another embodiment of a stand-alone ALIFimplant 2200. Implant 2200 comprises a base portion 2210 and a pluralityof secondary fastener portions, namely, secondary fastener portions2250, 2253, 2257, and 2259. Each of these secondary fastener portions isconfigured to be received in a corresponding fastener opening formedwithin base portion 2210 and is configured to engage with a fastener,such as a bone screw, such that the respective secondary fastenerportion is positioned in between the fastener/bone screw and the baseportion 2210. In this manner, an implant, such as a stand-alone ALIFimplant, another spinal implant, or another biomedical implant, may beprimarily formed from a relatively non-threadable material, such assilicon nitride, and the secondary fastener portions 2250, 2253, 2257,and 2259, which may comprise a more-readily threadable material, such astitanium or another metal, may be threaded to serve as an interfacebetween the bone screws 10 and the base portion 2210. In the depictedembodiment, secondary fastener portions 2250, 2253, 2257, and 2259comprise sleeves having a cylindrical shape.

One or more of the various fastener openings may comprise a groove 2255that may engage with a protrusion or another similar engagementstructure formed on one or more of the secondary fastener portions 2250,2253, 2257, and 2259 to prevent the secondary fastener portion(s) fromrotating once installed. In some embodiments, groove 2255 may comprisean area of a fastener opening where the material defining the opening isnaturally missing due to the exit angle of the fastener opening and theshape of the device in that region. Alternatively, a groove may beformed that would not otherwise be present in order to accommodate aprotrusion or other similar engagement feature. An example of aprotrusion on a secondary fastener portion for engaging groove 2255 canbe seen in FIG. 24 at 2455 and is discussed in greater detail below. Ofcourse, in alternative embodiments, a groove may instead be formedwithin a secondary fastener portion and may engage a correspondingprotrusion formed within one or more of the fastener openings.

In preferred embodiments, base portion 2210 is made up of a firstmaterial and each of secondary fastener portions 2250, 2253, 2257, and2259 is made up of a different material such that implant 2200 may takeadvantage of the different characteristics of the two differentmaterials in the same implant. For example, in some preferredembodiments, base portion 2210 may comprise a silicon nitride ceramicmaterial, another similar ceramic material, or another material that isnot readily subject to receiving stable threads for use in fixation tovertebral bones without damaging the implant, and secondary fastenerportions 2250, 2253, 2257, and 2259 comprise other materials moresuitable for being threaded and/or engaging a threaded fastener, such astitanium metals, titanium alloys, or other metals.

As shown in the cross-sectional view of FIG. 23, secondary fastenerportion 2250 may comprise an engagement feature 2251 configured toengage with a corresponding engagement feature 2211 of the base portion2210. In the embodiment depicted in FIG. 23, the engagement feature 2251of the secondary fastener portion 2250 comprises a protruding rim 2251,and the engagement feature 2211 of the base portion 2210 comprises aslot 2211 formed within a bone screw/fastener opening 2252. In someembodiments, slot 2211 may extend ail of the way around a perimeter ofopening 2252. Alternatively, slot 2211 may only be formed in one or morediscrete locations within the perimeter of opening 2252. In suchembodiments, rotation of the secondary fastener portion may berestricted by the interface between the rim/engagement feature of thesecondary fastener portion and the slot/engagement feature of the baseportion.

Secondary fastener portion 2250 further comprises an internal thread2253. In certain preferred embodiments, internal thread 2253 may extendabout an internal periphery of the secondary fastener portion 2250between about one turn and about two turns.

FIGS. 24-26 depict alternative embodiments of secondary fastenerportions comprising sleeves that may be used as individual interfacesbetween a fastener opening of a portion, such as a base portion, of animplant and a bone screw or other fastener. FIG. 24 depicts a first suchsleeve 2450. Sleeve 2450 comprises an internal thread 2453, aspreviously described. Sleeve 2450 further comprises a protruding rim2451, as also previously described. Rim 2451 may allow sleeve 2450 to befixedly engaged within a corresponding slot or similar engagementfeature of a portion of an implant.

Sleeve 2450 also comprises a plurality of partial slits 2457 formed atregular intervals about sleeve 2450. Partial slits 2457 may allow sleeve2450 to flex in desirable manners during installation of sleeve 2450 ina particular fastener opening of an intervertebral or other implant. Inparticular, slits 2457 may be flexed inwardly to allow rim 2451 todecrease in diameter and thereby allow rim 2451 to be seated within aslot or another engagement feature of an implant.

Sleeve 2450 further comprises a protrusion 2455 that extends radiallyfrom an exterior surface of sleeve 2450. Protrusion 2455 may beconfigured to be received in a groove formed within a fastener openingof an implant, or a part of an implant. For example, protrusion 2455 maybe configured to fit within groove 2255 of implant 2200. Protrusion 2455and groove 2255 are examples of means for preventing a sleeve or anothersecondary fastener portion from rotating with respect to a base portionor another portion of an implant. Another such example is one or moreslots, such as slot 2211, that are formed in one or more discretelocations within the perimeter of a fastener opening, along with acorresponding protrusion or protrusions formed on a sleeve or anothersecondary fastener portion.

FIG. 25 depicts another alternative embodiment of a secondary fastenermember comprising a sleeve 2550. Sleeve 2550 comprises an internalthread 2553 and a protruding rim 2551, as previously described. Sleeve2550 further comprises a single full slit 2557 that extends all the wayalong the length of sleeve 2550 in one location such that sleeve 2550comprises a split-ring sleeve. As with partial slits 2457 in sleeve2450, slit 2557 may allow sleeve 2550 to flex inwardly to allow rim 2551to decrease in diameter and thereby allow rim 2551 to be seated within aslot or another engagement feature of an implant.

FIG. 26 depicts yet another alternative embodiment of a secondaryfastener member comprising a sleeve 2650. Sleeve 2650 comprises aninternal thread 2653 and a protruding rim 2651, as previously described.However, sleeve 2650 lacks the slits previously described.

FIG. 27 depicts another alternative a stand-alone ALIF implant 2700.Implant 2700 comprises a base portion 2710 and a secondary fastenerportion 2750. In preferred embodiments, base portion 2710 and secondaryportion 2750 comprise different materials such that implant 2700 maytake advantage of the different characteristics of the two differentmaterials in the same implant, as previously described.

Implant 2700 is similar to implant 2100 in most respects However, unlikeimplant 2100, implant 2700 comprises teeth on both base portion 2710 andsecondary portion 2750. Moreover, washers 2730 may be provided inbetween base portion 2710 and secondary portion 2750. In someembodiments, washers 2730 may comprise an intermediate material, such asPEEK (polyetheretherketone), or another material that may comprise amore desirable interface between the material of base portion 2710(which, in some embodiments, comprises a relatively non-threadablematerial) and the material of secondary portion 2750 (which, in someembodiments, comprises a relatively more threadable material).

As with implant 2100, implant 2700 is configured such that secondaryportion 2750 may be coupled with base portion 2710 by way of two lockingmembers, namely locking member 2707 and locking member 2709. Theselocking members may comprise, for example, screws, bolts, pins, or thelike. In the depicted embodiment, locking members 2707 and 2709 arethreaded, and are received in corresponding threaded openings 2717 and2719, respectively, formed within opposing sidewalls of base portion2710.

Another pair of openings 2701 (only one of which is visible in FIG. 27)may be formed within a corresponding pair of recesses 2705 formed withinopposite ends of secondary portion 2750. Locking members 2707/2709extend through openings 2701 and openings 2717/2719 to couple secondaryportion 2750 with base portion 2710.

Although secondary portion 2750 is not shown as having bonescrew/fastener openings formed therein (i.e., similar to fasteneropenings 2152, 2154, 2156, and 2158), it should be understood that oneor more such openings may be formed therein if desired.

FIG. 28 depicts another embodiment of a stand-alone ALIF implant 2800comprising a base portion 2810 and a secondary portion 2850. Implant2800 further comprises locking member openings 2817 and 2819 formedwithin and extending along the entire length of opposing sidewalls ofbase portion 2810. Similar openings (not visible in FIG. 28) may beformed within opposing flanges 2886 and 2888 of secondary portion 2850such that two locking members 2807 and 2809 may be used to fixedlycouple base portion 2810 with secondary portion 2850. In someembodiments, washers 2830 may be used, either in between locking members2807/2809 and base portion 2810, or between base portion 2810 andsecondary fastener portion 2850. In addition, as previously mentioned inconnection with implant 2700, although secondary portion 2850 is notshown as having bone screw/fastener openings formed therein (i.e.,similar to fastener openings 2152, 2154, 2156, and 2158), it should beunderstood that one or more such openings may be formed therein ifdesired.

FIG. 29 depicts still yet another embodiment of a stand-alone ALIFimplant 2900 comprising a base portion 2910 and a secondary fastenerportion 2950. Implant 2900 is similar to implant 1000 in that itcomprises locking member openings 2990 and 2992 formed adjacent to adistal end of opposing sidewalls of base portion 2910. However, theselocking member openings 2990 and 2992, both of which are configured toreceive a pin 2983 or another locking member, extend horizontally ratherthan vertically.

In addition, rather than comprising recesses formed by opposing portionsof secondary fastener portion 2950, secondary fastener portion 2950comprises two opposing flanges 2986 and 2988 that are configured toextend around opposing exterior surfaces of a portion of base portion2910 defining openings 2990 and 2992. In this manner, secondary fastenerportion 2950 may be coupled with base portion 2910 by extending opposingflanges 2986 and 2988 around the opposing tips of base portion 2910 suchthat openings 2990/2992 are aligned with openings 2980 and itscorresponding opening on the opposite side (not visible in FIG. 29), andinserting pins 2983 or other locking members through the alignedopenings on both sides of implant 2900. Pins 2983 may be secured withinthese openings by a friction fit or may be threaded.

It will be understood by those having skill in the art that changes maybe made to the details of the above-described embodiments withoutdeparting from the underlying principles presented herein. Any suitablecombination of various embodiments, or the features thereof, iscontemplated.

Any methods disclosed herein comprise one or more steps or actions forperforming the described method. The method steps and/or actions may beinterchanged with one another. In other words, unless a specific orderof steps or actions is required for proper operation of the embodiment,the order and/or use of specific steps and/or actions may be modified.

Throughout this specification, any reference to “one embodiment,” “anembodiment,” or “the embodiment” means that a particular feature,structure, or characteristic described in connection with thatembodiment is included in at least one embodiment. Thus, the quotedphrases, or variations thereof, as recited throughout this specificationare not necessarily all referring to the same embodiment.

Similarly, it should be appreciated that in the above description ofembodiments, various features are sometimes grouped together in a singleembodiment, figure, or description thereof for the purpose ofstreamlining the disclosure. This method of disclosure, however, is notto be interpreted as reflecting an intention that any claim require morefeatures than those expressly recited in that claim. Rather, inventiveaspects lie in a combination of fewer than all features of any singleforegoing disclosed embodiment. It will be apparent to those havingskill in the art that changes may be made to the details of theabove-described embodiments without departing from the underlyingprinciples set forth herein. The scope of the present invention should,therefore, be determined only by the following claims.

1. An intervertebral spinal implant, comprising: a base portion; and asecondary portion comprising at least one opening configured to receiveat least one fastener for engaging a vertebral body of a patient'sspine, wherein: the secondary portion wholly defines a front end wallsurface of the intervertebral spinal implant; the base portion and thesecondary portion collectively define at least one of an upper surfaceand a lower surface of the intervertebral spinal implant; and the atleast one opening comprises a plurality of protrusions positioned alonga surface of the at least one opening that engage with respectiverecessions positioned about a proximal portion of the at least onefastener.
 2. The intervertebral spinal implant of claim 1, wherein theplurality of protrusions are defined by two opposing ramped surfaces. 3.The intervertebral spinal implant of claim 2, wherein the two opposingramped surfaces lead to a central portion of each protrusion of theplurality of protrusions.
 4. The intervertebral spinal implant of claim3, wherein the central portion comprises an at least substantially flatsurface.
 5. The intervertebral spinal implant of claim 3, wherein thetwo opposing ramped surfaces each comprise a flat surface positioned atan angle with respect to the central portion.
 6. The intervertebralspinal implant of claim 2, wherein the two opposing ramped surfaces eachcomprise a concave surface.
 7. The intervertebral spinal implant ofclaim 1, wherein the plurality of protrusions are arranged in a helicalpattern about the surface of the at least one opening.
 8. Theintervertebral spinal implant of claim 7, wherein the helical patternsubstantially matches a corresponding helical pattern of threads of theat least one fastener.
 9. The intervertebral spinal implant of claim 7,wherein the plurality of protrusions are tapered such that the height ofeach of the plurality of protrusions increases from a proximal portionof the at least one opening to a distal portion of the at least oneopening.
 10. The intervertebral spinal implant of claim 1, wherein therespective recessions are arranged in a helical pattern or a circularpattern.
 11. The intervertebral spinal implant of claim 1, wherein theat least one fastener is a bone screw.
 12. The intervertebral spinalimplant of claim 11, wherein the respective recessions are positioned ina threaded section of the proximal portion of the bone screw.
 13. Theintervertebral spinal implant of claim 11, wherein the respectiverecessions are positioned in an unthreaded section of the proximalportion of the bone screw.
 14. The intervertebral spinal implant ofclaim 1, wherein the base portion comprises a first material and thesecondary portion comprises a second material that is distinct from thefirst material.
 15. An intervertebral spinal implant, comprising: a baseportion comprising a plurality of openings and a plurality of secondaryfastener portions comprising at least one protrusion on an outer surfaceconfigured to be received in a groove formed within the plurality ofopenings in the base portion and a plurality of protrusions positionedalong an inner surface configured to engage with respective recessionspositioned about a proximal portion of a respective fastener, wherein:each of the plurality of secondary fastener portions is configured to bereceived in one of the plurality of openings in the base portion, andeach of the secondary fastener portions is configured to engage with therespective fastener such that the respective secondary fastener portionis positioned in between the respective fastener and the base portion.16. The intervertebral spinal implant of claim 15, wherein the baseportion comprises a first material and the plurality of secondaryfastener portions comprise a second material distinct from the firstmaterial.
 17. The intervertebral spinal implant of claim 15, whereineach of the plurality of secondary fastener portions comprises aninternal thread which extends about an internal periphery of eachrespective one of the plurality of secondary fastener portions betweenabout one turn and about two turns.
 18. The intervertebral spinalimplant of claim 15, wherein the plurality of protrusions are defined bytwo opposing ramped surfaces and a central portion formed between theopposing ramped surfaces. 1S. The intervertebral spinal implant of claim15, wherein the plurality of protrusions is arranged in a helicalpattern about the inner surface of each of the plurality of thesecondary fastener portions that substantially matches a correspondinghelical pattern of threads of the respective fastener.
 20. Theintervertebral spinal implant of claim 15, wherein the respectivefastener is a bone screw and the respective recessions are positioned inan unthreaded section of the proximal portion of the bone screw.